Cooled boiler casing



Jan. 29, 1946.

D. M. SCHOENFELD COOLED BOILER CASING Filed Jan. 1, 1942 l2 Sheets-Sheet2 1 INVENTOR.

TTOPNEY WSW.

Patented Jan. 29, 1946 cooLEn oILER cAsING David M. Schoenfeld, NewYork, N. Y., assigner to Combustion Engineering Company, Inc., NewYYork, N. Y.

Application January 1, 1942, Serial No. 425,281

(o1. 11o-56) This invention relates to improvements i-n 7 Claims.

steam boiler casings yand particularly to casings for boilers operatingunder forced draft, such as marine boilers.

In marine boilers, especially those in ships that may encounterpoisonous or noxious gases,

it has been found desirable where air is drawn from outside the ship forcombustion within the boiler furnace to isolate it from the air withinthe boiler room. Ordinarily the boiler has been surrounded by a gastight casing separated from the setting to provide space into which thecombustion air is delivered to circulate around the setting and thenpass via the burner openings into the furnace. Where the air has beenheated by uegases in an air heater, it has heretofore been usual to passheated air from the heater through the space between casing and boiler.Because of the arrangement of the connection between the air' preheaterand the casing this air took the path of least resistance to theburners, thereby short-circuiting some portions of the setting so thatair under pressure Was not present to seal all parts of the boilersetting where gases might flow outwardly into the fire room. Because ofits temperature this concentration of preheated air has required theoutside of the casing to be heavily insulated so as to maintain itsouter wall at a satisfactory temperature.

An object of this invention is to provide an improved gas tight casingspaced froml a boiler setting in combination with an air heater. Thisand other objects will be best understood upon consideration of thefollowing description of an embodiment of the invention when read inconjunction with the accompanying drawings, illustrating the inventionapplied to a marine boiler.

Figure 1 is a horizontal sectional View through a marine boiler on lineI--I of Fig. 2;

Figure 2 is a diagrammatic elevation on line 2 2 of Fig. 1;

Figure 3 is a diagrammatic elevation on line 3-3 of Fig. 1;

Figure 4 is a sectional elevation of a portion of the boiler unit online 4 4 of Fig. 1 showing a cross section through the air heater.

Referring to Fig. 1, the boiler comprises a furnace I having openings IIto mount burners projecting through one side wall 33 for introducingfuel and air. 'Ihe products of combustion pass over banks I2, I3 ofsteamV generating tubes and an intervening superheater I4 to the boilerofftake I5 at one end of the boiler. Located in the .offtake is an airheater I6 (Fig. 4), comprising tubes 20 connected into upper and lowertube sheets 2h22 and mounted vertically -so that gases from oitake I5pass through the tubes into the boiler 'flue 23. A baffleV 24intermediate the tube sheets ZI, 22 servesto divide the usual transverseair passsage into an upper pass '25 and a lower pass 26 connectedserially at one end by a conduit 21. The ai-r for combustion isdelivered to the air inlet chamber 28 by a fan, not showmand thegreaterpart passes through the passes 25, 26 to the 'air outlet chamber29 and thence via a conduit 38 l(Fig. 2) to the burner openings II.

As shown in Fig. 1 the boiler is enclosed in a composite wall 3iextending from `the offtak-e where the air preheater I6 is locatedacross the front or burner side, around the end 'opposite the offtakeand back thereto across the rear wall and also over the top of theboiler. The Acomposite wall 'is kmade up of an inner refractory lining32 backed by insulation 33 and a steel casing 34. Spaced outwardly fromthe wall 3l is a second or outer wall casing 35 lined with insulationand also extending around the three sidesv and also over the top of theboiler. The casings 3l, 35 and `particularly the latter which forms theouter wall, are made gas-tight so that no gas that may be between themcan enter the boiler room.

A5 may be seen in Fig. 2 the space 39u between the inner and outer wallson the burner side of thel boiler is subdivided into severalconduit-like channels by partitions 40, 4I extending yalong and betweenthese walls 3i, 35 from the offtake I5 at the vertical location of thebaffle plate 24 and lower tube sheetl 22, respectively, of' preheaterI6. These partitions terminate short of the end walls opposite theolitake and are inter connected by a plate 42 thereby forming a verticalchannel43 placing the upper conduit 44 in communication with they lowerconduit 45, the intervening conduit 30 being connected at one end withthe preheater outlet '29 for directing y heated air to the burneropenings II as previously mentioned. The upper channel 44 receives coolair from inlet lchamber 28 of thev air preheater I6 through an opening46 (Figs. 2 and 4) at the lower corner of the inner side Wall-41 (Fig.2) of the preheater. The bottom of the heated air outlet chamber 29overlies one end of conduit 45 and has holes 48 for air to flow fromconduit 45 into chamber 29 and thence to the burner openings II viayconduit 30.'

Some air from the channels 44, 45 and their intermediate branch 43 owsthrough the space 50 between the inner and outer endY walls that extendsacross the top and end of the boiler to o,

the side wall opposite the burner openings I I. At

the side opposite burner openings II a partitionV 49, extendinghorizontally (Fig. 3) from the end of the boiler opposite the oiftake I5ata vertical location intermediate the baie 24 and lower tube 'sheet 22and a parallel partition 5I below this air into the furnace, and a gasofftake at one end of the furnace; a casing around and spaced Y fromsaid boiler along the front and rear walls and extending overthe top andacross the end wall opposite said offtake whereby an air chamber isformed; a multi-pass air preheater so arranged Y in said Yofftake thatits air inlet and outlet are tube sheet form .three conduit channels 52,53,54.

Each ofthe channels `52, 53, 54 A tively, with conduit 2'I which directstheeair from the first to the second passl 26` of the'airheater. Inoperation cool air is delivered to inlet chamber 28 of the preheater I6,the major part pass- Y ingV through to the outlet chamber 29 and/thencevia conduit 30 directly to the air registers of Vburner openings I I.Because of the relatively vhigh temperature of thispreheated air, theinsulation on the outer casing adjacent conduit 30 will be relativelythick. Arr'minor. part of the air passes from-inlet chamberV 28 throughopening 46 (Figs. 2 and 4) intofthe upper channel 44 of the front wall,thence via channels 43 and 45 and throughv holes 48 into the outletchamber 29. Some of this air passes from channels 44, and

Y branch channel 43 through the space across thetop and end wall (Figs.2 and 3) into the three channels 52, 53, 54 ofthewall opposite burneropenings II and thence through the respective holes 55, 56, and 5I,Yinto the conduit 2'I connecting the rst and second passesfof the heater.

Since the part of the air passing around the boiler between the innerand outer walls is heated only to the extent that it absorbs heat as itcools the setting, the insulation onthe outer casing adjacent thechannels throughA which this air circulates need not be as thick as thatadjacent the hot'airconduit 30 which receives preheated air. Thecirculation of air Athrough the channels is caused by the differences inpressure existing be-Y tween the inlet chamber` 28 and the conduit 2'Iat lthe end of the first pass andtheoutlet cham- Y ber 29. TheV amountof air iiowing to seal and cool the setting may be determined by thearea of the holes 48, 756, 51 .y between the respective channels andtheair heater chambersZ'I, 29, or by other known means'such as dampers 60,6|at opening 46vand in conduit Y21. Because of this control over thedistribution of the air around the setting and the use ofv coldvair, thespace between outer casing and settingV wall may be reduced in depth andless outer insulation utilized thereby effecting a saving in space andweight. WhatIclaim is: U Y e Y 1. Ina steam boiler having a furnaceincluding a front wall formed with openings for'introducing tition meansin said casing extendingalong said Vfront wall to form aconduit/leadingthrough said air chamber from the outletY of said preheater to saidfront wall openings; and means closing said conduit adjacenttherend'wall oppositersaidxofftake- 1 --f g i Y I i i Y. ,2.4In'a steamboiler having a furnace including a' front-.wall formed with openingsfor introducing located adjacent the front wall of said boiler andcommunicate with the portion of said air chamber along said front wallat the oiftake end thereof and so that an interpass duct of saidpreheater is located adjacent said rear wall and communicates with theportion of said air chamber along the rear wall at the oiitake endthereof; partition Vmeans extending along said front wall in said Yairchamber 'tof form a conduit leading through said airY chamber from theoutlet of said preheater to said front 'wall openings; and means closingsaid conduit adjacent the end wall opposite said offtake. Y g f `3,.In asteam boiler having a furnace including a front wall iormedrwithopenings for introducing air into the furnace, and a gas ,oiftake atgoneend of the furnace; a hollow wall extending along the front of theboiler to form an air chamber; a multi-pass air preheater so arrangedvin said cfftake that its, air inlet'and outlet are located adjacent thefront wall of said boiler andcommunicate directly with the V,portion ofsaid air chamber along saidfront wall at the oitake end thereof;partition means in said rcasing-extending along said front wall to forma conduit leading centrally through said air chamber from the outlet-ofsaid preheater to said front Wall openings;

a partition closing said conduit adjacent the end wall opposite saidofftake, said partitionbeing spaced from said endv wall to ,form achannel for airto flow from the part of said air chamber above said,conduit tothe part therebelow.

4. vIn a steam boiler having aV` furnace including a front wall formedwith openings for introducing air into;the furnaceand a gas-oiftakeatione end of the furnace; -a vcasing around and spaced from said boileralong the front and rear walls and extending over thetop vand across'theend wallopposite said otake whereby an air chamber is formed; amulti-pass'airpreheater so arranged in said oiftake that its Aair inletVand outlet are located adjacent the front wallv of ksaid boiler chamberalong said front/'wall above Asaid conduit` in communicationwith'thesaid preheater inlet; a partition in said air chamber spaced fromrtheendV wall opposite said offtakeclosingsaidconduit and forming a passagefrom the portion'of said air chamber along said front wall'above saidconduit in communication with the portion thereofrlcelow-said conduit;Vand means placing the said last portion of said air chamberincommunication with said conduit in advance` of said front wall openings;

. 5. In--a steam boiler. having a furnace including a frontwall-formedwith openings for introducing Y air` into the furnace, agasofftake duct communi- Y enveloping said furnace and "said elements;

outer wall spaced from said inner wally to form an air chamber;partitions dividing said chamber into channels for circulating cool airabout the setting and into a conduit arranged to convey heated air fromsaid heater outlet to said front wall openings; means delivering coolair to said air heater and to said channels; and means connecting saidchannels to the air passages of said air heater at locations beyond itsair inlet in the direction of air flow therethrough; and means forcontrolling the iiow of air through said respective channels into saidair heater.

6l In a steam Iboiler having a furnace including a front Wall formedwith openings for introducing air into the furnace, and a gas offtake atone end of the furnace; means forming a casing around and spaced fromthe boiler along the front and rear side walls and extending over` thetop and across the end Wall opposite said oitake whereby an air chamberis formed; a multi-pass air heater so located in said ofltake that itscold air inlet and hot air outlet are disposed adjacent the front Wallin communication with the air chamber therealong; partitions in saidcasings along said front wall in said air chamber dividing said chamberinto a conduit in said front wall for conveying hot air :from saidheater outlet to said burners and channels for conveying cold air aroundsaid conduit to the outlet of said air heater thence to said front Wallopenings. 7. In a steam boiler having a furnace including a front wallformed with openings for introducing air into the furnace, and a gasoiftake at one end of the furnace; a multi-pass air heater in saidoii'take having a cold air inlet and a hot air outlet adjacent saidfront wall and an interpass duct adjacent the rear boiler Wall; meansforming an air chamber encasing said boiler along the front and rearwalls and extending over the top and across the end wall opposite saidoitake; partitions dividing said chamber to form front wall channels andcommunicating roof, end and rear wall channels for circulating airtherethrough; means closing the end of a channel on said front Wall toform a conduit leading through said chamber conveying hot air from saidheater outlet to said front wall openings; means delivering cold air tothe inlet of said air heater and another channel in the front wall;means connecting the roof, end and rear wall channels to said inter-passduct of said air heater and said front wall channel to said air heateroutlet,

DAVID M. SCHOENFELD.

